The molecular tool CRISPR/Cas allows introducing DNA double strand breaks into any gene of interest consequently resulting in stochastic mutations at the site of the target gene. However, precise gene repair through the application of a rescue construct suffers from limited efficiency. Researchers at Heidelberg University have now found a solution for this problem. Applying their new approach on the model organism medaka, the researchers laid the groundwork for easily integrating the repair copy of a defective gene into the DNA. As developmental biologist Prof. Dr. Joachim Wittbrodt explains, this efficient process makes precise genome editing possible in basic research, bringing the tool much closer to its application in medical treatment. The research results were published in eLife.